1. Field of the Invention
The invention pertains to a hopper loader apparatus for separating and forming an overlapping shingled stream of individual signatures of sheet materials from a vertically aligned, parallelepiped shaped stack of such signatures. The separated, individual signatures may then be subjected to subsequent handling operations.
2. Description of the Prior Art
It is usual in the graphic arts that sheet materials such as newspapers, books, printed cartons and the like emerge from a printing operation in a serial stream of partially overlapping signatures in shingled form. Such a stream of signatures is typically collected on a conveyor and moved to a stacker for aligning. The stacker receives the sheets in a serial mode from the conveyor and forms a neatly aligned stack for removal and transportation. While large numbers signatures can be conveniently handled in stack form, some operations on the signatures can only be performed individually. It therefore becomes necessary to separate individual signatures from a stack for individual treatment. The present invention pertains to a vertical hopper loader for separating individual signatures, which are substantially vertically aligned on a folded edge, from a stack of signatures and then forming an overlapping shingled stream of individual signatures.
It has been a problem in the art to provide an efficient and effective means of separating a stack into its individual signatures for presentation to other equipment, such as a packer box on a binder line. In the past, a stacked pile of printed signatures has been moved or pushed on a horizontal conveyor to an upwardly moving conveyor. Such an operation has many disadvantages since the stack does not reliably separate into evenly spaced overlapping individual signatures. This unevenness inevitably leads to downstream signature jams and misfeeds requiring considerable operator attention.
Complicated signature feeding equipment is known in the art. In this regard, U.S. Pat. No. 4,973,038 discloses a signature handling apparatus, however, this disclosure uses a horizontal feed conveyor which requires a stack pusher. The signatures tend to slide down a second ramp conveyor and hence require a retainer wedge. U.S. Pat. No. 4,049,260 shows an apparatus for feeding sheets having a horizontal entry conveyor and a ramp conveyor with an abrupt transition to an exit conveyor. U.S. Pat. No. 5,282,613 discloses a signature stream feeding apparatus which requires three conveyors. Likewise U.S. Pat. Nos. 4,008,890 and 3,945,633 discloses a signature stream feeding apparatus which requires three conveyors. Signatures moved by prior art three conveyor hopper loaders also have an abrupt transition between an upwardly directed ramp conveyor and a generally horizontal exit conveyor. As a result, they tend to follow a path propelled tangentially to the upwardly inclined ramp conveyor. This leads to an irregular signature stream. The complicated nature of the construction and mode of operation of known on-edge signature supply assemblies increases the probability of a jam or other malfunction during operation of the signature supply assemblies. In addition, the more complicated the construction of the signature supply assembly, the greater will be the cost of construction.
It has also been a problem in the art to reliably provide an efficient and effective means of separating a stack into its individual signatures and run reliably with a large range of signature sizes. The paper stock may range from heavyweight to lightweight and from a few pages per signature to many pages per signature. This difference in paper weight and/or pagination has required the operator to perform many adjustments to make the machine ready for a production run. The present invention seeks to simplify hopper loader construction, reduce costs and avoid or reduce problems encountered in the prior art. In prior art equipment, a stacked pile of printed signatures has been moved on a horizontal conveyor to an upwardly moving conveyor. Such an operation has many disadvantages since the stack does not reliably separate into evenly speed overlapping individual signatures which also leads to down stream signature jams and misfeeds. Difficulties in operating vertical loaders arise in that a large quantity of signatures cannot be loaded in the loader without interfering with the feeding of signature at the supply station, and the loaders cannot handle very short and very long signatures without substantial changes in the feeding mechanism. Further, the signatures are subjected to a constant riffling, sliding and jostling action that results in damage to the folds on the signatures when they move between conveyor belts. The present invention provides a vertical loader which avoids or reduces problems encountered in the prior art. The invention provides an apparatus for separating individual signatures which are substantially vertically aligned on a folded edge from a stack of signatures and then feeding them to subsequent processing equipment. According to the present invention there is provided a hopper loader which has only two conveyors, a downwardly inclined entry conveyor and an exit conveyor. The exit conveyor has an upwardly inclined planar ramp segment, an arched transition segment, and a planar exit segment. The arched transition segment has either a belt slide or a plurality of serially arranged rollers such that the arched transition segment has a radius of curvature sufficiently large such that a signature has a greater tendency to follow a path of the arched transition segment than to be propelled tangent to the upwardly inclined planar ramp segment. This smooth transition produces a regular, even signature stream. Individual signatures flow reliably, one-by-one downwardly out of the pocket to bindery equipment. The simplified equipment is economical, mobile, and signature size changeovers are easy to accomplish.
These and other features, advantages and improvements will be in part discussed and in part apparent to one skilled in the art upon a consideration of the detailed description of the preferred embodiment and the accompanying drawings.